Be mindful of the first year of New52.
DC had recently dropped the comics code and editorial wanted to show readers that comics were different now.
So the first few months saw lots of graphic content. Especially in the first issues.
They toned back down by the time Rebirth came along, though.
Appreciate that heads-up. Thanks
I just found this thread and was about to say the same thing! That’s actually my favorite comic ever.
I say comic as if it’s not 3 separate comics lol
I can’t think of stories that people haven’t already said for your kid, but I can say some that you should avoid with your son.
Definitely keep your son away from the Vertigo imprint and the Wildstorm imprint. Super violent, several curse words, and minor nudity.
Now while I prefer adult comics, these are just definitely not for younger kids.
I stand corrected!
The Impulse series from the ‘90s-early 2000’s is REALLY good! It fueled my obsession with Impulse lol
Some suggestions from me, a year later because thread necro 
My aim was to be appropriate for kids around 7. I do personally love a lot of the girl characters, which your son might not be into, but hopefully one day he’ll be ready to take a chance on them!
As other have said, Tiny Titans
If you are mostly reading to him, just pick a character you can kind of do the voice for.
The Batman 66 early comics (and perhaps others from 2013) feature movement progression within one panel, so that will probably appeal to a youngster